This invention relates in general to fluid seals for use in sealing a rotating shaft member. More particularly, the invention relates to an improved radial lip shaft seal of the type having an elastomeric body bonded to a metal case in which the contacting surface of the lip is made of polytetrafluoroethylene, and an apparatus for incorporating the radial lip shaft seal into unitized seals.
There are already in existence various types of radial lip seals, some of which use polytetrafluoroethylene (PTFE) for at least one of the lips. However, all of the known designs where the PTFE lip is the primary lip sealing the oil, have the free end of the radial lip facing the oil side of the sealed region. This makes it very difficult to install onto circular shafts, necessitating the use of special fixtures and special assembly precautions to assemble such seals on shafts so as not to nick or damage the surface of the PTFE material and destroy the functionality of the seals. This is because fluoroplastic materials are very susceptible to nicking or other surface damage to the contacting surface which compromises their ability to seal effectively.
A seal failure is critical in modern seal mechanisms even though the seal itself may be substantially less expensive than most other system components. However, the damage potential in event of seal failure is large, especially where the seal is located in an inaccessible location as is common in many modern compact and complex machines.
There has also been found a need for so-called unitized seals, that is, seals which incorporate both the seal and the counter wear surfaces, commonly known as the wear sleeve. The seal and the wear sleeve components are combined into a single assembly or xe2x80x9cunitizedxe2x80x9d. By pre-assembling these components together, proper dimensional installation is achieved, protection against nicking or other damage during handling is avoided, prelubrication, if desired, may be insured, and correct dimensional tolerances may be controlled at the point where the seal is manufactured as opposed to the point at which the other parts are manufactured or assembled.
None of the prior art patents teach a PTFE primary lip seal which does not require special fixtures and/or special assembly precautions to prevent damage to the seal surface and which provide a solution to this problem.
These and other objects and features of the invention will become apparent from the description and especially taken in conjunction with the accompanying drawings illustrating the invention.